This invention relates to a trigger to activate a supercoolable aqueous salt solution wherein the trigger and solution are encased within a flexible container to form a heat pack.
Heat packs utilizing supercoolable aqueous salt solutions have been used for some time for the treatment of soreness of muscles of athletes and sportsman in localized areas. From the simple hot water bottle we have progressed upward to the use of supercoolable aqueous salt solutions wherein the temperatures can be controlled as well as the duration of the heat given off. Various solutions such as sodium acetate and calcium nitrate tetrahydrate are examples of such solution.
In the past the scraping of metal to metal has initiated crystalization of the solution or inserting a crystal in the solution has also been used.
With the advent of the invention by Messrs Stanley and Hoerner of a trigger as setforth in U.S. Pat. No. 4,077,390 and the trigger of Messrs. Kapralis and Krukle as setforth in U.S. Pat. No. 4,379,448, a new means has been found to initiate the crystalization of the solution. In the case of U.S. Pat. No. 4,077,390 a trigger of a metal strip that is flexible which includes a number of fissures therein has been used. The trigger is placed in the heat pack container with the solution and the pack is sealed. To initiate the crystalization the trigger is flexed and as presently understood the flexing produces minute continuances of the fissures and these continuances or fractures will initiate the action.
The Kapralis et al U.S. Pat. No. 4,379,448 modified the teachings of U.S. Pat. No. 4,077,390 by placing slits on the inside of the trigger with none of them extending the to marginal edges of the strip. In addition, the inventors claim the permanent positioning of the trigger in a set spot, such as the corner of the pack.
Each of the above triggers have to some extent proved faulty. This is particularly true of U.S. Pat. No. 4,077,390 where continual bending to initiate crystallizaion has created a breaking of the triggers along the line of the slits or cuts. This results in failures of the triggers and in some cases the broken metal can cause punctures in the heat pack and leakage of the salt solution.